Is Duterte serious about a South China Sea red line?

Philippine President Rodrigo Duterte is as mercurial as Trump: He has in the past threatened to ride a jetski to disputed islands in the South China Sea and plant a flag to keep China at bay but he also claimed to be Chinese as part of his ongoing flattery of the Chinese leadership.

Today, the Associated Press reports that “the Philippines warned China that it will go to war over natural resources in the South China Sea — and it identified other ‘red lines’, or actions, Manila would find unacceptable.”

What is the future of the South China Sea, and what part will the Philippines play? Here are a few recent clues:

• Philippines island construction: the island nation itself “has started repairing a runway and upgrading other facilities on Thitu Island, the South China Sea territory that was last year the scene of a stand-off between Chinese and Philippine vessels,” according to the South China Morning Post.
• On the weekend, China’s military announced that two of its warships had challenged two United States Navy vessels that sailed within 12 nautical miles of the Paracel Islands, one of the disputed features of the South China Sea. The New York Times reports (paywall) that a Chinese defense ministry spokesperson said the U.S. had “gravely violated Chinese sovereignty.”
• The Asia Maritime Transparency Initiative’s Island Tracker is a free database of satellite photos and information about occupied and reconstructed islands and rocks in disputed areas of the South China Sea. Sadly, this is going to become an essential resource in the coming years.